Apparatus and method for sterilizing container closures

ABSTRACT

An apparatus ( 1 ) for sterilizing container closures comprises a conduit ( 2 ) defining a passage for the closure and having a wall ( 3 ) surrounding the passage, spraying means ( 4 ) for injecting inside the conduit ( 2 ) a sterilization fluid heated and vaporized, drying means for introducing hot air in the conduit ( 2 ) and means for heating the wall ( 3 ) of the conduit ( 2 ) operatively coupled thereto. A method for sterilizing container closures transported inside a conduit ( 2 ) having a wall ( 3 ) defining internally a passage for the closures comprises the steps of injecting inside the conduit ( 2 ) a sterilization fluid heated and vaporized, introducing hot air in the conduit ( 2 ) for drying the closures and heating the wall ( 3 ) of the conduit ( 2 ) by transferring heat directly to the conduit wall ( 3 ).

TECHNICAL FIELD AND BACKGROUND ART

The present invention relates to an apparatus and a method for sterilizing container closures.

As generally known, in the food industry and in particular in the field of aseptic filling of containers with beverages and in the field of aseptic food packaging, there exists a need to sterilise the containers both internally and externally before they are filled.

Sterilisation is generally achieved using chemical agents, e.g. hydrogen peroxide, which can be used on surfaces of every type, such as paper, plastic, metal or organic materials.

To ensure that filling takes place in aseptic conditions it is necessary to sterilise not only the containers but also their closures, for example caps or stoppers, which serve to seal the containers at the end of the filling process.

In this light, known apparatuses for sterilizing container closures comprise a conduit having a wall defining internally a passage for the closures.

Hence, said known apparatus defines inside the conduit a closed volume having a controlled aseptic atmosphere. Said known apparatus comprises spraying means for injecting inside the conduit a sterilization fluid (i.e. a chemical agent) heated and vaporized, and drying means for introducing hot air in the conduit.

The drying means have the function of eliminating the sterilization fluid condensed on the closures, before the closures themselves exit the apparatus.

It is noteworthy to observe that the sterilization fluids which are commonly used in these apparatuses are chemically active when their temperature is above a threshold value (activation value).

For this reason, the sterilization fluid is heated before it is injected in vaporized fashion inside the conduit. In this light, the apparatus comprises a device for heating and vaporising the sterilization fluid, for instance as described in patent application WO2006128884 of the same applicant.

Because the whole volume inside the conduit must be aseptic, the need arises of securing that the whole amount of fluid present inside the conduit be at a temperature above the activation value.

Thus, it is desirable that also the sterilization fluid that is condensed on the internal surface of the wall of the conduit be active (i.e. above the activation threshold).

For this purpose, in the operation of the sterilization process, the enthalpy of the process fluids (i.e. the sterilization fluid and the drying air) is regulated taking account of the fact that a portion of said enthalpy is needed to heat the conduit wall.

Therefore, in the known apparatus the process fluids (i.e. the sterilization fluid and the drying air), which are oriented towards the closures in order to treat them as described above, heat the fluid filling the volume internal to the conduit 2, and thus indirectly heat the conduit wall 3.

However, this known apparatus has the following drawbacks.

First of all, in the known apparatus the process fluids are not optimized for the treatment (i.e. sterilization) of the closures; in fact, the use of a portion of the enthalpy of the process fluids to obtain the heating of the conduit wall is a waste of energy.

In addition, a use of process fluids which is excessive with regard to the sterilization purposes (excessive with regard to either the flow rate or the temperature of the process fluids themselves) determines a risk of damaging the closures; in fact, en excessive heat is transferred to the closures; in particular, the temperature of the process fluids is too high.

A further problem arises in relation to the need of getting rid of the exhaust fluids which exit from the conduit. In fact, the exhaust, fluids exiting from the conduit would flow into the environment surrounding the conduit, if the exhaust fluids were not captured.

In this light, it is noteworthy to observe that the standards fix the threshold values (which must not be exceeded) for the concentration of the exhaust fluids in the environment of the sterilization conduit (in fact, said environment is itself kept aseptic).

Therefore, the sterilization apparatus comprises a system for the extraction of the exhaust fluids, from the conduit, in such a way that they do not flow in the environment.

In the known apparatus, an exhaust tube is provided, which is connected to a suction pump at one end and directly to the conduit at the opposite end. In this way, a suction force is directly applied to the volume inside the conduit.

This technical solution has the drawback to generate undesired flows of the process fluids inside the conduit, thus altering the distribution of the process fluids inside the conduits.

Therefore, the distribution of the process fluids inside the conduit is not optimized because it is affected by the suction force applied by the system for extracting the exhaust fluids.

DISCLOSURE OF THE INVENTION

An object of the present invention is to eliminate the aforesaid drawbacks and to make available an apparatus and a method for sterilizing container closures, which is particularly efficient and optimizes the use of the process fluids with respect to the sterilization of the closures.

An additional object is to make available an apparatus and a method for sterilizing container closures which has reduced operation costs.

Said objects are fully achieved by the apparatus of the present invention, which is characterised by the content of the claims set out below.

BEST MODE FOR CARRYING OUT THE INVENTION

These and other features shall become more readily apparent from the following description of a preferred embodiment, illustrated purely by way of non limiting example in the accompanying drawing tables, in which:

FIG. 1 shows the apparatus according to the present application, in perspective view;

FIG. 2 shows the apparatus of FIG. 1, in a different perspective view;

FIG. 3 shows an enlarged view of the portion A of FIG. 2;

FIG. 4 shows the apparatus of FIG. 1, in a further perspective view;

FIG. 5 shows an enlarged view of the portion B of FIG. 4;

FIG. 6 shows a functional diagram pertaining to the method according to the present patent application;

FIG. 7 shows the apparatus according to the present application including the system for the extraction of the exhaust fluids, in lateral view;

FIG. 8 shows an enlarged view of a first operative portion of the apparatus of FIG. 7;

FIG. 9 shows the portion of FIG. 8, in a perspective view;

FIG. 10 shows an enlarged view of a third operative portion of the apparatus of FIG. 7;

FIG. 11 shows the portion of FIG. 10, in a perspective view;

FIG. 12 shows an enlarged view of portion C of FIG. 7;

FIG. 13 shows an internal portion of the apparatus of FIG. 7.

With reference to the Figures, the numeral 1 globally designates an apparatus for sterilizing container closures, such as caps or stoppers, which serve to seal the containers and are applied to the containers at the end of the filling process.

The apparatus 1 comprises a conduit 2 which defines a passage for the closures.

The conduit 2 has at least one wall 3; in particular, the conduit 2 has a lateral wall 3 which surrounds the passage for the closures.

The conduit 2 has, in the illustrated example, a rectangular section; accordingly, the wall 3 comprises four faces, each having substantially flat shape.

In addition, the conduit 2 is preferably arranged along a longitudinal direction.

However, such a configuration of the conduit 2 is not essential; in fact, the conduit 2 may have a different shape, for example a tube having a wall 3 with circular section and arranged on a curved path.

Inside the conduit 2 a conveyor is arranged (not shown in the figures) to transport the closures form an inlet to an outlet of the conduit 2 itself. Said inlet and outlet correspond to the inlet and outlet of the apparatus 1. The apparatus 1 receives (singularly) at the inlet the closures to be sterilized and makes available the same closures at the outlet after their sterilization.

The closures inside the conduit 2 are preferably arranged with their bottom wall face up and their concave portion face down.

The apparatus 1 also comprises a plurality of nozzles 4 coupled to the conduit 2 for injecting a sterilization fluid inside the conduit 2.

The apparatus is also provided with a system for heating and/or vaporizing the sterilization fluid, in order to feed the nozzles 4 with sterilization fluid which is heated above the activation temperature for that fluid and is vaporized. Such a system, not shown in the figures, is described in patent application WO2006128884 of the same applicator, which is here incorporated by reference.

Therefore, the nozzles 4, together with said system (i.e. the system for heating and vaporizing the sterilization fluid), define spraying means for injecting inside the conduit 2 a sterilization fluid heated and vaporized.

Said sterilization fluid is preferably Vapour of Hydrogen Peroxide (VHF).

In particular, the spraying means comprises a first delivery pipe 5, which is arranged inside the conduit 2. The first delivery pipe 5 is provided with a plurality of holes along its length, which define the nozzles 4. The first delivery pipe 5 is fed with the sterilization fluid (heated and vaporized as described above) at one of its ends and is closed at an opposite end (said closed end is indicated with the reference number 6 in the figures).

Furthermore, the apparatus 1 comprises drying means for introducing hot air in the conduit, for the purpose of removing the sterilization fluid condensed on the closures.

In the preferred embodiment illustrated in the figures, the drying means comprises a second delivery pipe 7, which has a structure similar to that of the first delivery pipe 5 (i.e. is arranged inside the conduit 2 and has a closed end) but is fed with heated air (or any inert gas).

Therefore, the drying means is configured to provide a flow of hot air able to intercept the closures passing inside the conduit 2. Said air tubes are connected to a source of heated air, and aseptic filters are inserted downstream the source of heated air, to secure that the environment inside the conduit 2 is kept aseptic. The drying means are coupled to the conduit 2 substantially downstream with respect to the spraying means, in the direction of movement of the closures inside the conduit 2.

In this light, it is important to observe that the conduit 2 preferably defines three operative portions, which are arranged consecutively along the path followed by the closures in their movement inside the conduit 2.

A first operative portion is provided with the first delivery pipe 5 (and thus with the nozzles 4), i.e. it is the portion where the spraying means is active.

A third operative portion is provided with the second delivery pipe 7, i.e. it is the portion where the drying means is active.

A second operative portion, intermediate between the first and the second operative portion, is a portion where neither the spraying means nor the drying means is directly active on the closures (i.e. neither the first delivery pipe 5 nor the second delivery pipe 7 is arranged in the second operative portion of the conduit 2).

In addition, the apparatus 1 originally comprises means for heating the wall 3 of the conduit 2 (i.e. the wall 3 surrounding the passage for the closures to be sterilized), which are operatively coupled thereto.

Said heating means are preferably coupled to at least one of the faces of the wall 3 of the conduit 2 on its whole length, i.e. along the path followed by the closures in their movement inside the conduit 2. Hence, the heating means are coupled to at least one face of the wall 3 of all of the three operative portions of the conduit 2 described above.

This feature has the advantage that length of the second operative portion of the conduit 2 may be set to a desired value (said length having an influence on the overall performance of the apparatus 1 and thus being a parameter to be optimized) and the flow of the process fluids (i.e. sterilizing fluid and drying air) set independently at a desired optimized value, the wall 3 of the conduit 2 (including the second operative portion of the conduit 2) being heated independently with respect to the process fluids.

In the preferred embodiment of the apparatus 1, illustrated in the figures, said means for heating the wall 3 of the conduit 2 comprises a heating layer 8 attached to the external surface of the wall 3. This layer 8 is provided with a plurality of electric resistors.

Thus, the electric resistors are associated to the heating layer 8 attached to said external surface of the wall 3.

In particular, said layer 8 comprises a plurality of stripes having an adhesive surface to be coupled to the faces of the wall 3 of the conduit 2. The electric resistors are associated to said stripes, according to a known technique.

Therefore, at least an electrical resistor is directly coupled to an external surface of the wall 3 of the conduit 2, providing a heater of the wall 3 itself directly coupled thereto. The heater (the electric resistors) is connected to an electric power source 9, and transfers directly to the wall 3 of the conduit 2 the heat generated by virtue of Joule effect.

In particular, the apparatus 1 comprises a plurality of electric resistors connected in parallel to the electric power source 9.

It is noteworthy to observe that said power source is independent from said spraying means and drying means (i.e. the sterilization fluid and the drying air have are not used for heating the conduit wall).

The latter feature is particularly important, because it allows to heat the conduit wall 3 without interfering with the sterilization process, which is regulated by the process fluids (i.e. the sterilization fluid and the drying air).

It also has to be noted that the heater is coupled to the conduit 2 in such a way as to maximize the portion of wall 3 where heat is exchanged.

In the preferred embodiment illustrated in the figures, the conduit wall 3 has a to transparent portion 10 for inspecting the interior of the conduit 2 (and in particular the closures conveyed inside the conduit 2).

In this light, said heater (i.e. the layer 8 provided with the electrical resistors) is operatively active on the whole remaining portion of the conduit wall 3.

It is noteworthy to observe that the means for heating the wall 3 of the conduit 2, according to an alternative embodiment not shown in the figures, comprises a duct (or a plurality of ducts) wherein heating fluid is pumped, the duct being arranged in contact with the conduit wall 3, thus providing a heat exchanger able to increase the temperature of the conduit wall. Said heating fluid may be taken form any heating source (preferably independent from the process fluids) and does not require to be filtered, since it does not come into contact with the aseptic environment internal to the conduit 2.

According to a further aspect of the present invention, the apparatus 1 is provided with a system for controlling the temperature of the wall 3 (provided with the heating means). The aim of this system is to maintain the wall temperature at a desired value avoiding any waste of energy. A further aim of this system is to monitor the means for heating the conduit 2, detecting possible faults and bad functioning.

In this light, the apparatus 1 comprises at least a sensor 11 (e.g. a thermocouple) coupled to the wall 3 of the conduit 2 to detect the temperature thereof, and an electronic card 12, which constitutes control means connected to the power source 6 and to the sensor 11 to regulate retroactively the power transferred to the heater (and therefore the heat transferred to the wall 3), in such a way that the temperature of the conduit wall 3 has a desired value (i.e. a reference value Tref).

Said desired value is not lower than the activation value of temperature of the chemical agent used as sterilization fluid. For example, said desired value for the temperature of the conduit wall ranges from approximately 50° C. to approximately 130° C., when VIP is used as sterilization fluid.

Preferably, the apparatus 1 comprises a plurality of sensors 11 coupled to different points of the conduit wall 3, to detect corresponding temperature values of the conduit wall. These detection points are preferably longitudinally spaced along the whole length of the conduit wall 3; more preferably, at least a sensor 11 is provided in correspondence to each of the three operative portions of the conduit 2.

In addition, each sensor 11 is preferably coupled to a portion of the wall 3 wherein a corresponding heater is coupled (where a plurality of heaters, each e.g. formed by a plurality of resistors, are arranged in parallel).

This is particularly important in combination with the fact that the means for heating the wall 3 comprises a plurality of heaters connected in parallel and arranged along the conduit aligned longitudinally.

In fact, in this way it is possible to detect if a portion of the wall 3 has a temperature lower than the rest of the wall (and maybe lower than the activation value). This may be caused by a fault of one of the heaters (e.g. one of the panels constituting the layer 8 of electric resistors).

In this case, the control means are configured to regulate the power transferred to the other heaters (the ones which are working properly) to maintain the desired temperature of the wall 3 (thus maintaining the wall 3 at a uniform and constant temperature), and at the same time for activating alert means in response to the detected fault condition.

It is noteworthy to observe that the power source 9 preferably comprises a source of continuous voltage (e.g. any alternate power source coupled to a rectifier or any other alternative solution) connected to a converter 13 defining a module for a PWM modulation of a voltage applied to the resistors.

In this light, the control means 12 are connected to said converter 13 in order to drive it in response to the result of the comparison between the reference temperature value (Tref) and the temperature values detected by the sensors 11 (as schematically shown in FIG. 6).

The apparatus 1 also comprises a system for capturing the exhaust fluids which exit from the conduit 2.

Such a system comprises exhaust openings 14 consisting of outlets defined in the upper portion of the wall 3 and preferably extending upwards.

These exhaust openings 14 cooperate with corresponding suction hoods 15 defined in a exhaust tube 16, wherein a suction pump is preferably inserted.

According to an alternative embodiment, the suction pump is substituted with an exhaust tube 16 defining a vertical column in correspondence to the exhaust openings 14, in such a way to provide an adequate natural draught.

It is noteworthy to observe that the exhaust opening 14 is arranged at a predetermined distance from the lower end of the correspondent suction hood 15; therefore, the exhaust tube 16 is not directly connected to the conduit 2.

Preferably, a plurality of exhaust openings 14 and correspondent suction hoods 15 is provided; in the illustrated embodiment three openings 14 and correspondent suction hoods 15 are provided, each suction hood 15 being arranged in correspondence of a respective operative portion of the conduit 2.

Preferably, the suction hood 15 has a section which is larger than the section of the correspondent exhaust opening 14.

Such a feature allows to provide a step of capturing the exhaust fluids exiting from the exhaust opening 14 of the conduit 2 and shifting laterally while moving upwards.

In this way, the exhaust fluids present inside the exhaust opening 14 are captured by way of a suction principle analogous to that of a hood draught (e.g. the draught of a hood provided in a professional kitchen to capture the fumes produced by the cooking).

In addition, each suction hood 15 is provided with means for adjusting the effective section of the suction hood 15 itself.

These means for adjusting the effective section of the suction hood 15 (illustrated in FIG. 13) comprises preferably a fist flange 17 and a second flange 18 arranged inside the suction hood 15 in contact with each other and in such a way to be rotated one with respect to the other.

Said fist flange 17 and second flange 18 define apertures 19 which increase or decrease their overlap as a function of the reciprocal angular position of the fist flange 17 and second flange 18.

Thus, when the overlap of corresponding apertures 19 of the flanges 17 and 18 is minimum, the effective section of the suction hood 15 is accordingly minimized; likewise, when the overlap of corresponding apertures 19 of the flanges 17 and 18 is maximum, the effective section of the suction hood 15 is accordingly maximized.

Alternatively to or additionally to said means for adjusting the effective section of the suction hood 15, means are provided (not illustrated because itself known) to vary the power applied to the suction pump inserted in the exhaust tube 16, with the possibility to control said means (e.g. the pump may be driven by an electric power source through an inverter controlled by an electronic card).

It is noteworthy to observe that such a distance (between the upper end of the exhaust opening 14 and the lower end of the correspondent suction hood 15), the effective section of the suction hood 15 and the ratio between the section of the upper end of the exhaust opening 14 and the section of the lower end of the correspondent suction hood 15 (the former section being smaller than the latter section) constitute parameters which are set in order to minimize the effect of the system for extracting exhaust fluids from the conduit 2 on the distribution of the fluids contained inside the conduit.

In such a way, the fluid-dynamic distribution of the process fluid inside the conduit 2 is not affected by the extraction of the exhaust fluids; in fact, the exhaust fluids are captured by way of a draught principle, and no suction force is directly applied to the fluid contained inside the conduit 2.

Such a result improves the performance of the apparatus, because it avoids undesired flows of process fluids inside the conduit 2, and thus it allows to control the distribution of the process fluids inside the conduit 2 optimizing their effect on the closures.

It is further object of the present invention a method for sterilizing container closures transported inside a conduit 2 haying a wall 3 defining internally a passage for the closures.

Said method comprises the following steps:

-   -   injecting inside the conduit 2 a sterilization fluid heated and         vaporized (VHP);     -   introducing hot air in the conduit for drying the closures,     -   heating the wall 3 of the conduit 2 by transferring heat         directly to the conduit wall.

It is noteworthy to observe that the heating step entails the heating the wall 3 on the whole length of the conduit 2, thus heating all of the three operative portions of the conduit 2.

Preferably, in the heating step, the heat is transferred to the wall 3 from a heat source which is independent from the process fluids (i.e. said sterilization fluid and said drying air).

In particular, the heating step entails the transmission of energy from a power source independent from said spraying means and drying means to at least a heater directly coupled to an external surface of the conduit wall 3.

Preferably, said heater is an electrical resistor (or a layer 8 attachable to the wall 3 and provided with a plurality of resistors connected with each other) and said power source is an electric power source; in this light, the heating step entails the transmission of electrical energy from the electrical power source to said at least a heater.

The method further comprises a step of detecting at least a value of the temperature of the conduit wall 3, and a step of regulating retroactively the power transferred to the heater, in such a way that the temperature of the conduit 2 wall 3 has a desired value (as described above with respect to the apparatus 1). Preferably, the sterilization fluid is VHP and said desired value for the temperature of the conduit wall ranges from approximately 50° C. to approximately 130° C.

Said detection step preferably entails the coupling of a plurality of sensors 11 to different points of the conduit wall 3, to detect corresponding temperature values of the conduit wall. More preferably, the detecting step entails the detection of at least a temperature value in correspondence of each of the three operative portions of the conduit 2.

In addition, preferably the heater is defined by layers 8 comprising electrical resistors and attached to the external surfaces of the conduit 2 wall 3.

In this light, said regulating step entails a PWM modulation of a voltage applied to the resistor.

It is noteworthy to observe that the heating step, according to an alternative embodiment, comprises a step of pumping a heating fluid (i.e. a hot fluid) through a duct (or a plurality of ducts) arranged in contact with the conduit wall 3, thus providing a heat exchange (from the heating fluid to the wall 3) in order to increase the temperature of the wall 3 of the conduit 2.

In fact, the heat transferred in the heating step may be transferred by a conduction principle (heat transferred to the wall 3 e.g. from electric resistors directly coupled to the wall itself) or by convection principle (heat transferred to the wall 3 e.g. from a heating fluid conveyed along a surface, and in particular the external surface, of the wall itself).

The method according to the present application further comprises a step of extracting exhaust fluids from the conduit 2.

Such an extracting step entails a step of arranging a plurality of consisting of outlets defined in the upper portion of the conduit 2 wall 3 and extending upwards (defining exhaust openings 14), cooperating with corresponding suction hoods 15 defined in a exhaust tube 16, wherein a suction pump is inserted (according to the description above of the apparatus 1).

Hence, the extracting step consists of capturing the exhaust fluids by way of a draught principle.

The extracting step further comprises a step of adjusting the effective section of the suction hoods 15.

Such an adjusting step entails preferably the rotation of a fist flange 17 with respect to a second flange 18, these flanges being arranged in contact with each other inside the suction hood 15, in such a way to be rotatable one with respect to the other. Said fist flange 17 and second flange 18 define apertures 19 which increase or decrease their overlap as a function of the reciprocal angular position of the fist flange 17 and second flange 18 (according to the description above of the apparatus 1).

It is noteworthy to observe the upper end of the exhaust opening 14 is arranged at a predetermined distance from the lower end of the correspondent suction hood 15.

Such a distance (between the upper end of the exhaust opening 14 and the lower end of the correspondent suction hood 15), the effective section of the suction hood 15 and the ratio between the section upper end of the exhaust opening 14 and the section of the lower end of the correspondent suction hood 15 (the former section being smaller than the latter section) constitute parameters which are set in order to minimize the effect of the system for extracting exhaust fluids from the conduit 2 on the distribution of the fluid contained inside the conduit. Hence, the method according to the present application further comprises a step of adjusting these parameters to minimize the effect of the system for extracting exhaust fluids from the conduit 2 on the distribution of the fluid contained inside the conduit 2. without modifying any fluid-dynamics equilibrium.

The invention described above provides the following advantages.

The apparatus and method for sterilizing closures according to the present invention allow to maintain the wall 3 of the conduit 2 at a desired temperature value (above the activation value of the sterilization fluid injected in the conduit) independently on the operation of the process fluids (i.e. the sterilization fluid and the drying air injected in the conduit 2).

Therefore, the temperature and the flow rate of the process fluids are optimized for the sterilization of the closures, thus avoiding waste of energy and any risk of damaging the closures.

In addition, the apparatus and method for sterilizing closures according to the present invention allow an optimization of the energy used to heat the conduit wall and provide a control system able to achieve an automatic regulation and detection (also providing alert signals) of possible faults in the heating of the conduit wall.

The apparatus and method for sterilizing closures according to the present invention further allow to provide a uniform and constant temperature of the conduit wall, thanks to said control system in combination with the presence of a plurality of sensors coupled at different points of the conduit wall for multiple temperature detection.

A further advantage is to improve the performance of the apparatus avoiding undesired flows of process fluids inside the conduit 2, and thus allowing to control the distribution of the process fluids inside the conduit 2 optimizing their action on the closures.

Such a result is possible because, in the step of extracting the exhaust fluids, the exhaust fluids are captured by way of a draught principle (hence no suction force is directly applied to the fluid contained inside the conduit 2), thus allowing the fluid-dynamic distribution of the process fluid inside the conduit 2 not being affected by the extraction of the exhaust fluids. 

1. Apparatus (1) for sterilizing container closures, comprising: a conduit (2) defining a passage for the closures and having a wall (3) surrounding the passage; spraying means (4) for injecting inside the conduit (2) a sterilization fluid heated and vaporized; drying means for introducing hot air in the conduit (2), characterized in that it comprises means for heating the wall (3) of the conduit (2) operatively coupled thereto.
 2. Apparatus according to claim 1, wherein said means for heating the wall (3) of the conduit (2) comprises at least a heater (8) coupled to an external surface of the wall (3) and connected to a power source (9) independent from said spraying means and drying means.
 3. Apparatus according to claim 2, wherein said heater (8) is an electric resistor connected to an electric power source (9).
 4. Apparatus as claimed in claim 3, wherein said means for heating the wall of the conduit comprises a plurality of electric resistors connected in parallel to said electric power source (9).
 5. Apparatus according to any of the preceding claims, wherein the conduit (2) wall (3) has a transparent portion (10) for inspecting the interior of the conduit (2), and wherein said means for heating the wall (3) are configured for being operatively active on the whole remaining portion of the conduit (2) wall (3).
 6. Apparatus according to any of the preceding claims, comprising: at least a sensor (11) coupled to the conduit (2) wall (3) to detect the temperature thereof; control means (12) connected to the means for heating the wall (3) and to the sensor (11), to regulate retroactively the heat transferred to the wall (3), in such a way that the temperature of the conduit wall (3) has a desired value.
 7. Apparatus according to any of the preceding claims, wherein the means for heating the conduit (2) wall (3) is applied to the whole length of the conduit (2).
 8. Apparatus according to any of the preceding claims, comprising means (15,16) for capturing exhaust fluids from the conduit (2) having at least a suction hood (15) arranged over a corresponding exhaust opening (14) defined in the conduit (2) ad facing upwards, at a predetermined distance thereto.
 9. Apparatus according to claim 8, wherein the section of said suction hood (15) is larger than the section of the corresponding exhaust opening (14), to provide a capturing of the exhaust fluids by way of a draught effect.
 10. Method for sterilizing container closures transported inside a conduit (2) having a wall (3) defining a passage for the closures, comprising the following steps: injecting inside the conduit (2) a sterilization fluid heated and vaporized; introducing hot air in the conduit (2) for drying the closures, characterized in that it comprises a step of heating the wall (3) of the conduit (2) by transferring heat directly to the conduit wall (3).
 11. Method according to claim 10, wherein the heating step entails the transmission of energy from a power source independent from said spraying means and drying means to at least a heater (8) directly coupled to an external surface of the conduit wall (3).
 12. Method according to claim 11, wherein said heater is an electrical resistor and said power source is an electric power source, the heating step entailing the transmission of electrical energy from the electrical power source to said at least a heater.
 13. Method according to any claim from 10 to 12, comprising a step of detecting at least a value of temperature of the conduit (2) wall (3), and a step of regulating retroactively the heat transferred to the wall, in such a way that the temperature of the conduit wall (3) has a desired value.
 14. Method according to any of the preceding claims, comprising a step of capturing exhaust fluids exiting form the conduit (2), said capturing phase entailing a step of arranging at least a suction hood (15) over a corresponding exhaust opening (14) extending upwards from the conduit (2), at a predetermined distance thereto, to capture the exhaust fluids from the conduit 2 by way of a draught effect.
 15. Method according to claim 14, wherein the section of the suction hood (15) is larger than the section of the corresponding exhaust connection (14), to provide a step of capturing the exhaust fluids exiting from the exhaust opening (14) of the conduit (2) and shifting laterally while moving upwards. 